Re: SVG2 CR - Catmull-Rom curve commands missing??

Hey, folks,

I'm the person who originally suggested the Catmull-Rom path command. 
I'd love to see it added, as I think it would make a lot of authoring 
tasks much more straightforward.

If the browser makers express willingness to implement it, I'd be 
willing to write a spec just for that feature; that spec text could be 
published on its own, or folded into a larger SVG2.1 spec, or whatever. 
We'd also need tests for the feature; I could help with those, too, 
though I'd like help on that.

My initial suggestion was simply having some form of smooth curve that 
interpolates between control points, such that all the control points 
are on the line itself (unlike Beziérs); after a bit of research, I 
stumbled on Catmull-Rom curves as a reasonable solution to that.

The upside to using Catmull-Rom curves is that they provide pretty 
intuitive curves for a large range of variables (assuming you imply a 
duplicate starting point and ending point to the formula, and have a 
modest tension parameter), are fairly fast to compute (good for 
rendering and animation performance), and are widely used in computer 
graphics libraries; a downside is that the penultimate curve segment 
does change its shape when you add another point, but perhaps that's 
unavoidable.

Catmull-Rom is actually a set of variants within the class of cubic 
Hermite splines [1], and if someone has a better suggestion for a spline 
other than Catmull-Rom, I'm all ears; ideally, it would also be fast to 
calculate, and at least as stable as Catmull-Rom. At one point, someone 
from Adobe suggested that there might be a different/better curve 
formula, but they didn't state which one.

If there's a graphics expert out there who'd like to collaborate on 
finding the ideal spline and default variables (e.g. tension, etc.), 
please let me know.

[1] https://en.wikipedia.org/wiki/Cubic_Hermite_spline

Cheers,
Doug

On 11/12/18 3:13 AM, matshyeq wrote:
> Fully Agree!,
> 
> I heard some voices (eg. SVG standard being stalled blocking Inkscape 
> development) but I had no idea on the scale of stagnation.
> The original input requirements look awesome!
> and it's truly sad that any work still being done on it focuses rather 
> on throwing stuff out of scope just to quickly bump up the number.
> 
> While it could seem to be rational to release some important (?) changes 
> now rather than postpone the whole release
> it really works against the standard.
> Releasing half cooked stuff (or even worse: only some minor, cosmetic 
> changes) doesn't bring the incentive for adoption.
> Again, that's actually harming the standard - Check out XSLT2.0 support 
> by Microsoft or in browsers…
> 
> What is really surprising is that this is happening now, when first SVG 
> standard is finally very well supported (all browsers!, all vector 
> drawing software) and the industry is now awaiting a long list of 
> improvements 
> (https://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input).
> 
> On Sat, 10 Nov 2018 at 14:29, Dr. Olaf Hoffmann <dr.o.hoffmann@gmx.de 
> <mailto:dr.o.hoffmann@gmx.de>> wrote:
> 
>     Hello,
> 
>     almost all new features identified to be required in the beginning
>     of SVG 2
>     https://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input
>     are absent in the current draft:
>     https://www.w3.org/TR/2018/CR-SVG2-20181004/
> 
>     After all these years and compared to SVG 1.1 and SVG tiny 1.2 the
>     current
>     draft for SVG 2 looks like stagnation or even regression.
>     It is quite surprising, that it did not already simply end as a note
>     and work
>     on SVG is stopped completely.
> 
>     Alternatively, looking on the current draft for SVG 2, it seems to
>     be time now
>     to reject this and to start from the beginning with the list of
>     requirements
>     from 2012 ;o)
>     Else there is low chance, that authors and audience can enjoy new
>     features in
>     this century ;o)
> 
>      >Hello,
>      >
>      >What happened to this great idea?
>      >
>      >https://www.w3.org/TR/2015/WD-SVG2-20150409/
>     paths.html#PathDataCatmullRomCommand
>      >https://www.w3.org/Graphics/SVG/WG/track/actions/3085
> 
> 
>      >we wait 8 long years, hoping and only to find it missing now?
> 
>      >Thank you,
>      >Kind Regards
>      >~Msciwoj
>

Received on Monday, 12 November 2018 21:27:36 UTC